CCTag reproducible output

[anauta00]

Hi,

I have just started using your nice library. The results are encouraging and fast (on the GPU). 😀

However, I would like each 'detection run' to yield the same output. Now, each run shows small deviations in the center points found.

I have looked at the code but cannot seem to find out how to do this.

Can anyone help?

Thanks and greetings, Auke Nauta

[simogasp]

most probably it's because of some randomness of the algorithm in choosing points. Whenever a random function is used in the code, a deterministic seed should be used so that the result are consistent over multiple runs. This may require some refactoring, though. I cannot pinpoint the exact parts but if you are willing to do it, it could be a nice contribution. :)

[anauta00]

Hi,

I have researched this issue extensively now. Using the CPU, deterministic runs can be obtained by #defining 'CCTAG_SERIALIZE'.

However, for the GPU part, this is far from clear. I tried #defining 'SORT_ALL_EDGECOORDS_IN_EXPORT' but then CCTag would no longer compile: std::sort( _all_edgecoords.host.ptr, _all_edgecoords.host.ptr+all_sz, v_comp ); would not compile then...

As (at least some of) you have wrote the software, I would think (certainly hope!) that you could point me in the right direction. Having non-deterministic output (using the GPU) is not an option for my application.

Thanks for any help and greetings, Auke

[simogasp]

What is the compilation error for std::sort? @griwodz should know better what needs to be done.

[anauta00]

Hi,

function "int2cmp::operator()" cannot be called with the given argument list    CCTag   C:\Program Files\Microsoft Visual Studio\2022\Community\VC\Tools\MSVC\14.34.31933\include\xutility  1092    

Several such errors are generated for 'xutility' as well as 'algorithm'.

Predicate 'int2cmp' is defined like this:

class int2cmp
{
public:
    __host__
    inline bool operator()( const int2& l, const int2& r )
    {
        return tpcmp( l, r );
    }
};

[simogasp]

Could it be that _all_edgecoords is a short2 instead of a int2? Maybe trying to define a short2cmp the same way as int2cmp in cmp_list.h and then use it inside the std::sort could solve the issue?

[anauta00]

Thanks, that did the trick!

However, GPU output still is not deterministic. I tried lots of other things (like using the '--sync' switch) but to no avail. Unfortunately, my knowledge of CUDA programming is really limited and I can not get this to work (to my liking). Any additional help to create deterministic output would be appreciated!

Greetings, Auke

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